The present invention is directed to a method of positioning a radiology device.
Radiology devices generally comprise a tube for emitting an X-ray beam in a given direction, means for positioning at least one part of an object""s body in the X-ray beam, and X-ray sensitive means of reception of the beam after it crosses that part of the object""s body.
In angiography applications, for example, the blood vessels of a human body have the same absorption as the tissues surrounding them are thus invisible on the images obtained. An image is first taken without addition of a contrast medium, then an iodine-base contrast medium, for example, is injected into the blood of the human body, and a second image is taken after the contrast medium is properly distributed in the vascular system of the human body. The two images or series of images obtained being digitized by electronic means, an image subtraction is then carried out, making it possible to take away from the second image the organs visible on the first, that is, the organs naturally visible to X-rays, such as bones, etc.
It is known how to carry out two-dimensional vascular angiography. Now, it is very difficult to locate significant features such aneurysms, notably cerebral, which can be masked by other vessels or organs, by reason of the complexity of the extreme tangle of structures having to be visualized. If the operator manages to carry out this location, it is then difficult to visualize the features satisfactorily in order to determine their importance and/or gravity and, if necessary, the best way of attending to them. The operator is therefore led to repeat two-dimensional films at angles of incidence chosen at random or based on the operator""s own experience, which tends to increase the X-ray dose received by the human body and to make the success of angiography depend on the know-how of a given operator.
Methods of image acquisition with rotational positioning of the radiology device are also known. An image is acquired for each of the different angles of incidence. The images thus obtained can be treated, notably, by algorithms of the type used in computerized axial tomography to make a volume reconstruction of a system of arteries and veins. Depending on what the films taken at the first angles of incidence reveal, other acquisitions are made at new angles of incidence, which make possible a closer observation of the region concerned. The choice of those angles of incidence in space is difficult also by reason of the complexity of the region observed and because of the possible superposition of other vessels.
The angiography systems with three axes of rotation offer the possibility of making rotational dynamic acquisitions according to each of the axes in space. However, their possibilities remain poorly utilized because of the difficulty of their use, due to the fact that the three-dimensional orientation of the vessels is a priori unknown.
U.S. Pat. No. 5,699,446 proposes a method of image by positioning the radiology device to determine the best angles of incidence and, in particular, for positioning the detector parallel to the object having to be visualized. Two acquired reference images are used for that purpose at two different angles of incidence, in order to determine automatically the three-dimensional orientation of the vessel having to be examined. A triaxial apparatus is used, from determination of the angular positions of the first two axes, to position the third axis in a position parallel to the vessels. The rotation on the third axis is freely used to make the acquisitions.
Assisted by epipolar lines, the operator designates a segment on each view. The segment can then be reconstructed in three dimensions and an incidence proposed, so that the direction of the X-ray beam will be perpendicular to that segment. This method requires numerous manipulations and does not guarantee that the final incidence supplied will offer the best possible view of the organ.
The present invention is directed to a method for obtaining a specific image or images of a part an object body, e.g., a human body.
The method, according to an embodiment of the invention, is intended for a radiology device of the type comprising a means of emission of an X-ray beam and a means of reception of the X-ray beam, after it has crossed a part of the object""s body. A three-dimensional image of a part of the object""s body is reconstructed from a series of two-dimensional films. Two-dimensional views of the three-dimensional image are produced at different angles of incidences. The angles of incidence making possible the best visualization of the part of the object""s body are selected. The angles of incidence are stored in a memory.
The angles incidence are supplied to the radiology device for its positioning with a view to an intervention or procedure on the part of the object""s body under fluoroscopy allowing visualization in real time of two-dimensional films. The best angle of incidence found can thus found for monitoring the progress of the intervention or procedure.
In one embodiment of the invention, the memorization of the angles of incidence is stored in a radiology device memory.
The angles of incidence are advantageously supplied to the radiology device automatically.
In one embodiment of the invention the selection of the angles of incidence are made by processing of the three-dimensional image.
In another embodiment of the invention, the selection of the images is made by processing the angles of visualization of the three-dimensional image.
In order to avoid the risk of the radiology device striking the object""s body, it may be prevented from being positioned at angles where such risk might occur.